Hysteresis compensation for a digitizer tablet
First Claim
1. In a digitizer tablet having a pointing device, a method for determining and reporting the X-Y coordinates of the pointing device, relative to the tablet, corrected for pointing device movements, comprising the steps:
- (a) determining but not reporting the coordinate positions of the pointing device along a first coordinate axis during successive time points,(b) using the determined coordinate positions of step (a), based on the pointing device'"'"'s velocity and acceleration determined from said use, calculating the coordinate position along said first coordinate axis that the pointing device would assume at a future time point,(c) reporting the coordinate position calculated in step (b).
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Accused Products
Abstract
A digitizer tablet providing hysteresis compensation in which the X and Y coordinates of a pointing device are measured at different times. In order to enable the tablet to report X and Y coordinates that when displayed will more accurately reflect the pointing device movements, a correction algorithm, built, for example, into the controlling software, estimates and reports what the first measured coordinate would have been, measured when the second coordinate is measured, based upon the calculated velocity and acceleration of the pointing device. A similar technique can be used to correct the reported value of the second coordinate. In a preferred embodiment, constant coefficients of a linear equation having as variables three consecutive coordinate values or three consecutive preprocessed coordinate values are predetermined and used in the correction algorithm. The preferred embodiment integrates the velocity and acceleration hysteresis compensation into a three point recursive noise filter.
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Citations
22 Claims
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1. In a digitizer tablet having a pointing device, a method for determining and reporting the X-Y coordinates of the pointing device, relative to the tablet, corrected for pointing device movements, comprising the steps:
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(a) determining but not reporting the coordinate positions of the pointing device along a first coordinate axis during successive time points, (b) using the determined coordinate positions of step (a), based on the pointing device'"'"'s velocity and acceleration determined from said use, calculating the coordinate position along said first coordinate axis that the pointing device would assume at a future time point, (c) reporting the coordinate position calculated in step (b). - View Dependent Claims (2, 3, 4, 5)
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6. In a digitizer tablet having a pointing device, a method for determining and reporting the pointing device'"'"'s X-Y coordinates relative to the tablet corrected for pointing device movements, comprising the steps:
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(a) determining the coordinate positions of the pointing device along at least one of the X and Y axes during at least three successive time point t0, t1 and t2 to produce three corresponding positions p0, p1 and p2. (b) calculating a corrected value Pr for the pointing device coordinate position p2, where
space="preserve" listing-type="equation">P.sub.r =k.sub.2 p.sub.2 +k.sub.1 p.sub.1 +k.sub.0 p.sub.0,(c) reporting the corrected value Pr at a time t3, where k0, k1 and k2 are fixed constants determined by the time lag between t3 and t0. - View Dependent Claims (7, 8)
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9. In a digitizer tablet having a pointing device, the method for reporting the pointing device X-Y coordinates relative to the tablet corrected for pointing device movements, comprising the steps:
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(a) determining the coordinate positions of the pointing device along at least one of the X and Y axes during at least three successive tine points t0, t1 and t2 to produce three corresponding positions p0, p1 and p2, (b) determining from the time points and corresponding position points values representing the velocity and acceleration of the pointing device in moving from position p0 to p2, (c) calculating for a time point t3 a value p3 for the pointing device coordinate position which the pointing device will occupy at the time point t3, where t3 >
t2 >
t1 >
t0,(d) reporting the calculated value p3 at the time t3.
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10. In a digitizer tablet having a pointing device, the method for reporting its X-Y coordinates relative to the tablet corrected for pointing device movements, comprising the steps:
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(a) determining and storing the constant coefficients k2, k1, and k0 of an equation defining a corrected value, Pr, of an X or Y coordinate position, wherein the equation is of the form;
space="preserve" listing-type="equation">P.sub.r =k.sub.2 p.sub.2 +k.sub.1 p.sub.1 +k.sub.0 p.sub.0,and p0, p1, and p2 are measured coordinate values during consecutive time points, (b) determining the coordinate positions of the pointing device along at least one of the X and Y axes during at least three successive time points t0, t1 and t2 to produce three corresponding positions p0, p1 and p2, (c) evaluating the said equation using the stored constant coefficients and the determined positions. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A digitizer tablet having a pointing device, and means for reporting its X-Y coordinates relative to the tablet corrected for pointing device movements, said means for reporting comprising:
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(a) means for determining the coordinate positions of the pointing device along at least one of the X and Y axes during at least three successive time points t0, t1 and t2 to produce three corresponding positions p0, p1 and p2, (b) means for determining from the time points and corresponding position points values representing the velocity and acceleration of the pointing device in moving from position p0 to p2, (c) means for calculating for a time point t3 a value p3 for the pointing device coordinate position which the pointing device will occupy at a time point t3 >
t2 >
t1 >
t0,(d) means for reporting the calculated value p3 at the time t3. - View Dependent Claims (17)
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18. A digitizer tablet having a pointing device, and means for reporting its X-Y coordinates relative to the tablet corrected for pointing device movements, comprising:
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(a) means for storing the constant coefficients k2, k1, and k0 of an equation defining a corrected value, Pr, of an X or Y coordinate position, wherein the equation is of the form;
space="preserve" listing-type="equation">P.sub.r =k.sub.2 p.sub.2 +k.sub.1 p.sub.1 +k.sub.0 p.sub.0,and p0, p1, and p2 are coordinate values during consecutive time points, (b) means for determining the coordinate positions of the pointing device along at least one of the X and Y axes during at least three successive time points t0 t1 and t2 to produce three corresponding positions p0, p1 and p2, (c) means for evaluating the said equation using the stored constant coefficients and the determined positions to determine Pr, (d) means for reporting Pr. - View Dependent Claims (19, 20, 21, 22)
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Specification